Open62541 - Writing Array in Siemens Data Block

Question

In Open62541 in C++, I could not find in the documentation how to write data in a Data Block of a Siemens PLC, especially in the case of an array. With the UA_Client_writeValueAttribute(client, UA_NODEID_STRING(4,"DATABLOCK_NAME"."VARIABLE_NAME"), &value); I do not get any error message neither the variable change.

The PLC is the server and the code is running on a Raspberry Pi 4 as client.

Thanks for helping!

score 0 · Accepted Answer · answered Aug 25 '23 at 19:07

I was able to crack the answer! Here it is:

UA_Variant opcValue;
UA_Variant_init(&opcValue);
// Create an array of Float values
UA_Float dataArray[] = {1.1f, 2.2f, 3.3f, 4.4f, 5.5f};
size_t dataArraySize = sizeof(dataArray) / sizeof(UA_Float);

// Create a variant containing the array
UA_Variant_setArrayCopy(&opcValue, dataArray, dataArraySize, &UA_TYPES[UA_TYPES_FLOAT]);

// Write the array to the OPC UA variable
UA_NodeId nodeId = UA_NODEID("ns=NAMESPACE_INDEX;s=\"DATABLOCK_NAME\".\"VARIABLE_NAME\""); 

UA_StatusCode writeStatus = UA_Client_writeValueAttribute(client, nodeId, &opcValue);
if(writeStatus != UA_STATUSCODE_GOOD) {
    // Handle error
}

So, for my case was: UA_NodeId nodeId = UA_NODEID("ns=4;s=\"opcData\".\"Readings\"");

Open62541 - Writing Array in Siemens Data Block

1 Answers1